1. Field of the Invention
The present invention relates to a display device for displaying a picture image corresponding to an input signal on a light-shielding plate by selectively intercepting the light to be transmitted through a light-transmitting section provided through the light-shielding plate, depending on the input signal.
2. Description of the Related Art
Those hitherto known as the display device include, for example, cathode ray tubes (CRT) and liquid crystal display devices.
Those known as the cathode ray tube include, for example, ordinary television receivers and monitor units for computers. Although the cathode ray tube has a bright screen, it consumes a large amount of electric power. Further, the cathode ray tube involves a problem in that the depth of the entire display device is large as compared with the size of the screen.
On the other hand, the liquid crystal display device is advantageous in that the entire device can be miniaturized, and the display device consumes a small amount of electric power. However, the liquid crystal display device involves problems in that it is inferior in brightness of the screen, and the field angle of the screen is narrow.
In the case of the cathode ray tube and the liquid crystal display device, it is necessary for a color screen to use a number of picture elements (image pixels) which is three times a number of picture elements used in a black-and-white screen. For this reason, other problems occur in that the device itself is complicated, a great deal of electric power is consumed, and it is inevitable to cause an increase in cost.
In order to solve the problems described above, the present applicant has suggested a novel display device (see, for example, Japanese Laid-Open Patent Publication No. 7-287176). As shown in FIG. 38, this display device includes actuator elements 400 arranged for respective picture elements. Each of the actuator elements 400 comprises a main actuator element 408 including a piezoelectric/electrostrictive layer 402 and an upper electrode 404 and a lower electrode 406 formed on upper and lower surfaces of the piezoelectric/electrostrictive layer 402 respectively, and an actuator substrate 414 including a vibrating section 410 and a fixed section 412 disposed under the main actuator element 408. The lower electrode 406 of the main actuator element 408 contacts with the vibrating section 410. The main actuator element 408 is supported by the vibrating section 410.
The actuator substrate 414 is composed of ceramics in which the vibrating section 410 and the fixed section 412 are integrated into one unit. A recess 416 is formed in the actuator substrate 414 so that the vibrating section 410 is thin-walled.
A displacement-transmitting section 420 for obtaining a predetermined size of contact area with respect to an optical waveguide plate 418 is connected to the upper electrode 404 of the main actuator element 408. In the illustrative display device shown in FIG. 38, the displacement-transmitting section 420 is arranged such that it is located closely near to the optical waveguide plate 418 in the OFF selection state or the unselection state in which the actuator element 400 stands still, while it contacts with the optical waveguide plate 418 in the ON selection state at a distance of not more than the wavelength of the light.
The light 422 is introduced, for example, from a lateral end of the optical waveguide plate 418. In this arrangement, all of the light 422 is totally reflected at the inside of the optical waveguide plate 418 without being transmitted through front and back surfaces thereof by controlling the magnitude of the refractive index of the optical waveguide plate 418. In this state, a voltage signal corresponding to an attribute of an image signal is selectively applied to the actuator element 400 by the aid of the upper electrode 404 and the lower electrode 406 so that the actuator element 400 is allowed to make a variety of displacement actions in conformity with the ON selection, the OFF selection, and the unselection. Thus, the displacement-transmitting section 420 is controlled for its contact and separation with respect to the optical waveguide plate 418. Accordingly, the scattered light (leakage light) 424 is controlled at a predetermined portion of the optical waveguide plate 418, and a picture image corresponding to the image signal is displayed on the optical waveguide plate 418.
When a color picture is displayed by using the display device, the following operation is performed. That is, for example, light sources for the three primary colors are switched to control the light emission time for the three primary colors, while synchronizing the contact time between the optical waveguide plate and the displacement-transmitting plate with the cycle of color development. Alternatively, the contact time between the optical waveguide plate and the displacement-transmitting plate is controlled, while synchronizing the light emission time for the three primary colors with the color development cycle.
Therefore, the illustrative display device suggested by the present applicant is advantageous in that it is unnecessary to increase the number of picture elements as compared with the black-and-white screen, even when the display device is applied to a color display system.